In a wireless communications network, wireless communication devices (WCDs) communicate with one or more core networks (CNs) via one or more Radio Access Network(s) (RANs). A Radio Access Network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station (BS). In some RANs, the base station is called “NodeB” or “B node” or evolved NodeB (eNB). The base stations communicate via an air interface with WCDs within range of the base stations.
A WCD can be any device that has the capability to communicate wirelessly. Typically, the WCDs that connect to a cellular wireless communications network are smartphones, tablets, phablets, computers. However, it is expected that in the near future many things (e.g., household appliances, meters, vending machines, cars, buildings, etc.) will include WCDs—i.e., the things will be given the capability to wirelessly transmit data via a wireless network (e.g., a 3rd Generation Partnership Project (3GPP) 4G cellular network). Such things that have WCD capability are sometimes referred to as “cellular Internet-of-Things (CIoTs)” devices or just “Internet-of-Things (IoTs)” devices or “machine type communication (MTC)” devices or Machine-to-Machine (M2M) devices.
A 3GPP, Long Term Evolution (“LTE”) core network may include a core serving node (CSN) (i.e., an apparatus that provides network services to a WCD, such as, for example, an apparatus that implements one or more of: a Mobility Management Entity (MME), a serving GPRS support node (SGSN), an SGW, a PGW, a CIoT Serving Gateway Node (C-SGN)—a C-SGN is a logical entity that supports only the necessary functionality required for CIoT use cases—see 3GPP TR 23.720.0.1.0). The core network may also include a Home Subscriber Server (HSS) and a separate gateway node if the CSN does not implement gateway functionality or for roaming WCDs. The gateway node provides connectivity for the WCDs of the communication network to one or more external Packet Data Networks (PDNs). Some WCDs may have simultaneous connectivity with more than one network gateway node for accessing multiple PDNs. The network gateway node may be, for example, a Gateway GPRS Support Node (GGSN) or a PDN Gateway (PGW). Typically the network gateway provides PDN connectivity by creating a PDN connection for a radio terminal. The PDN connection may be requested by the WCD, for example, by sending a message to a core network node (e.g., MME). 3GPP WCDs use a protocol between the WCD and the CN called Non-Access Stratum (NAS). The NAS protocol is described in 3GPP TS 24.301 and 3GPP TS 24.008.